refactor: Streamline project configuration and styling

This commit simplifies the Vite configuration by removing unnecessary options like `base`, `sourcemap`, and custom `rollupOptions`. It also removes the explicit server port definition, allowing Vite to manage it.

Additionally, minor styling adjustments are made to the scrollbar in `index.html` and default values for select inputs in `AccountsPayableView` are updated for clarity. The `engines` property was removed from `package.json` as it's not strictly necessary for typical development workflows.

package.json

@@ -11,16 +11,13 @@
     "preview": "vite preview",
     "start": "node server.js"
   },
-  "engines": {
-    "node": ">=18.0.0"
-  },
   "dependencies": {
     "@google/genai": "^1.39.0",
-    "express": "^4.21.1",
     "lucide-react": "^0.454.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
-    "recharts": "^2.13.0"
+    "recharts": "^2.13.0",
+    "express": "^4.21.1"
   },
   "devDependencies": {
     "@types/react": "^19.0.0",